This application claims the priority of 199 12 963.0, Filed Mar. 23, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a system and a process for controlling an automatically shifting transmission for a vehicle.
In order to provide the driver of a vehicle with an automatic shift transmission in special situations with the possibility of directly influencing the selected transmission ratio, German Journal DE-Z Automobiltechnische Zeitschrift, Volume 6/1990, pages 308 to 319, the provision of, so addition to an automatic operation, a manual operation in that the driver can directly select individual gears of the step-type automatic system. For this purpose, parallel to a shifting channel for the automatic operation, a second shifting channel is provided for the manual operation so that the driver can cause, with a rocker-type movement of a shifting lever, can in each case cause a downshifting or upshifting by one gear. A similar system for continuous transmissions is known from Swiss Journal CH-Z Automobil Revue, Volume 51/1992, page 23.
Furthermore, it is known to cause gear shifts in a power-operated transmission by a selecting device from a steering wheel of a vehicle as seen, for example, German Journal DE-Z Auto Motor Sport, Volume 22/1991, Page 300.
In addition, DE 43 11 886 A1, A describes a system and a process for controlling an automatically shifting transmission. The control changes from an automatic operating mode to a manual operating mode when a position M is touched by way of a driving position switch or when, by way of a shifting rocker provided in the steering wheel, a shifting signal is emitted for a defined time period, for example, 0.7 seconds. The manual operating mode is exited again when an M position is touched again by way of the driving position switch or an upshift signal is emitted for a defined time period, for example, 1.5 seconds. Finally, the operating mode influenced by the driver may be caused to be exited if this operating mode had been active for a defined time period. However, on the whole, a change-over is always involved from the automatic to the manual operating mode and vice versa.
An object of the present invention is to provide a system and a process so that an automatically shifting transmission having a selecting device can be influenced by the driver for a short time.
According to the invention, this object has achieved by providing a control unit triggering the transmission being operable in two operating modes, the selection of the operating mode taking place by a first selecting device, in a first automatic operating mode, ratios of the transmission being adjusted essentially automatically according to operating values determined by generating devices and, in a second operating mode influenced by the driver, ratios of the transmission being adjusted essentially as a function of the signal of a first selecting device, characterized in that the control unit can be temporarily changed from the first operating mode, without the selection by the first selecting device by actuating the second selecting device, into the second operating mode.
For this purpose, the control changes from the automatic operating mode normally selected in a position D of the first selecting device (of the driving position switch), without any selection by the first selecting device, temporarily into the operating mode influenced by the driver when a second selecting device (a rocker or other signalling device) is actuated which is arranged on the steering wheel. In this case, it is particularly advantageous that this change-over requires no lasting exiting of the automatic operating mode.
The present invention is therefore particularly suitable for initiating a downshifting in front of a curve in the road or when entering a town. Following the brief direct influencing by the driver when selecting the transmission gear, the automatic operating mode becomes active again. In this case, the duration is preferably firmly set and preferably starts again with each actuation of the selecting device arranged on the steering wheel. However, it is also contemplated to make the election of the duration a function of operating parameters of the vehicle, such as the driving speed, the rotational speed or the transmission gear.
The operating parameters may also be replaced by a quantity evaluating the driving style. In addition, the present invention can be used independently of the selected construction of the transmission and can be used particularly for multi-step transmissions and infinitely variable speed transmissions. It is also independent of the spacial arrangement of the selecting devices and their construction.
A differentiating device, provided for analyzing the signals of the two selecting devices, defines one of two transmission ratio determination devices for the selection of the transmission ratio. One operating mode is assigned to each transmission ratio determination device. Preferably, two signal analysis devices and one change-over device are provided for this purpose. While the signal analysis devices are each assigned to a selecting device respectively and analyze its signals, the change-over device is responsible for the selection of the transmission ratio determination device, that is, the operating mode, as a function of the signals of the signal analysis devices.
Between the signal analysis device for the second selecting device and the change-over device, a time element is provided in the form of a switch-off delay. This time element provides that a signal of the second selecting device is maintained for a defined time period. It is particularly advantageous for the time element to be set back by a signal of a kick-down switch. As a result, by way of a kick-down, the first automatic operating mode can immediately be activated again, and there is no risk that the driver, for example, during a passing maneuver, does not initiate the required triggering of a transmission ratio change.
As an alternative or supplementary thereto, the time element receives a signal of a lateral-acceleration limit value generator and a signal of a drive/coasting detector. After the expiration of time, the time element will be set back only if there is a falling below a preadjusted amount of lateral acceleration and a drive operation exists at the same time. No drive operation also is to be detected when the vehicle is parked or is rolling without any operation of the accelerator pedal. As a result of this measure, for example, during a fast cornering, no change takes place from the manual to the automatic operating mode, and the manually selected transmission ratio is maintained in the coasting operation. This is particularly useful when driving downhill, when entering a town or when selecting the transmission ratio corresponding to the first gear in front of a red traffic light.
Furthermore, after a change of the operating mode by the actuation of the second selecting device, this actuation of the second selection device is not interpreted as a command for changing the transmission ratio. A change of the transmission ratio will then not take place before the next actuation of the second selecting device. As an alternative, after a change of the operating mode, the command for changing the transmission ratio is implemented immediately.